The present invention relates generally to an improved filter for a drum maintenance unit in an imaging system. More specifically, the invention relates to a reclamation system and process in an offset print imaging system that reclaims fluid and filters the fluid through a low friction, reduced fiber shed filter.
Offset ink jet printing systems having intermediate transfer surfaces are known. U.S. Pat. No. 4,538,156 to Durkee et al. discloses a system where an intermediate transfer drum is employed with a print head. A final receiving surface of paper is brought into contact with the intermediate transfer drum after the image has been placed on the intermediate drum by nozzles in the print head. The image is then transferred to the final receiving surface. A cleaning medium is then brought into contact with the intermediate transfer drum to prepare the surface of the drum prior to the next image being formed on the transfer surface.
U.S. Pat. No. 5,389,958 to Bui et al. discloses an offset ink jet printing system in which a liquid intermediate transfer surface is applied to the transfer drum. Nozzles in the print head then eject drops of ink onto the liquid intermediate transfer surface to form an ink image thereon. A final receiving substrate such as paper is then brought into contact with the intermediate transfer surface, and the ink image is transferred to the final receiving substrate. The liquid intermediate transfer surface is cleaned and reapplied prior to the next image being formed on the transfer surface.
Ink jet printing systems that use a liquid intermediate transfer surface generally require an applicator to apply the desired amount of liquid onto the intermediate transfer support surface. One such applicator of this type is disclosed in U.S. Pat. No. 5,808,645 to Reeves et al. This patent discloses an applicator that is housed in a replaceable transfer drum maintenance cassette.
U.S. Pat. No. 6,068,372 to Rousseau et al. also discloses a replaceable liquid application system for applying a liquid intermediate transfer surface to a support surface in a printer. The liquid application system is contained in a removable cassette and uses a liquid impregnated arcuate surface that engages the support surface by rolling contact. The liquid impregnated arcuate surface is contained in a removable cartridge in the cassette.
In the 372 patent, the cartridge also contains a reclamation assembly that extends the useful life of the cartridge. The reclamation assembly reclaims liquid from the support surface, filters the liquid by passing the liquid over a filter, and supplies the liquid back to the arcuate surface for reapplication to the support surface. Over time, however, the filter may become clogged with debris. Once clogged, the system will operate as if the filter did not exist. This will allow debris to reach the roller and cause problems.
Another replaceable liquid application system for applying a liquid intermediate transfer surface to a support surface in a printer is disclosed in co-pending U.S. patent application Ser. No. 10/740,461 filed Dec. 23, 2003. Like the 372 patent, the liquid application system is contained in a removable cassette and uses a liquid impregnated arcuate surface that engages the support surface by rolling contact. This system also includes a reclamation assembly that reclaims liquid from the support surface, filters the liquid by passing the liquid over a filter, and supplies the liquid back to the arcuate surface for reapplication to the support surface. The filter is a polyester felt and the transfer roller is of a polyurethane foam.